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A flying drone is a really solid idea for a Titan lander for a couple reasons: * The surface atmosphere density is higher than Earth's (1.5 atm) * Gravitation
by rzimmerman 7y ago
A flying drone is a really solid idea for a Titan lander for a couple reasons:
* The surface atmosphere density is higher than Earth's (1.5 atm)
* Gravitational force is much lower (0.15g)
* We don't know a lot about the surface composition or topography, so wheels and motors represent a challenge
* Visibility may be poor, making visual navigation tricky (though that's also a problem for a flying vehicle I suppose)
I've heard people ask about "why a nuclear power source?" Saturn is 10x as far from the sun as Earth, so sunlight is about 1/100th as bright. In addition, Titan's atmosphere blocks most of that. There really isn't any other realistic option.
I hope it works and they take videos.
- jvanderbot 7y agoThe data rate from the surface of titan is abysmal. Even with a relay, we won't get much video, but man, I hope we get some.
- maxxxxx 7y agoNo 4K flyovers for Instagram?
- jvanderbot 7y agoI mean sure, eventually, over many down link cycles. But not real time.
- spullara 7y agoSpace travel just makes it utterly clear there is on such thing as real time. Computing is constantly running up against the speed of light.
- aeorgnoieang 7y agoIn a sense tho, at-the-speed-of-light is real time, as it's the maximum speed of anything.
- pault 7y agoIf, as clock A nears the speed of light it appears that stationary clock B is slowing down, doesn't that mean that at the speed of light is no time? Does a photon in a vacuum arrive instantly at its destination? If a photon looks at another photon, does the other photon appear not to be moving at all, or... Ouch my brain.
- sq_ 7y agoNot completely related, but you reminded me of something interesting I remember hearing about neutrinos. Apparently (HN physicists please correct me if I'm wrong), neutrinos have an extraordinarily tiny objective lifetime, and the only reason we can detect them is that, because they travel so close to the speed of light, they experience almost no passage of time in while in flight.
- aeorgnoieang 7y ago> If, as clock A nears the speed of light it appears that stationary clock B is slowing down, doesn't that mean that at the speed of light is no time? If clock A could reach the speed of light (which it can't), then, yes, clock B would appear to be 'frozen in time'. > Does a photon in a vacuum arrive instantly at its destination? From the perspective of any possible observer, no, it always appears to be traveling at the speed of light. If an observer could travel at the speed of light (which it can't), then, yes, it would appear as if it arrived instantly in the sense that clocks at both its source and destination would appear to be not running at all. > If a photon looks at another photon, does the other photon appear not to be moving at all, or... Ouch my brain. Yeah, this is tricky. Photons can't look or see – what could that mean as looking/seeing involves detecting photons (or, in the sense that something like echolocation is 'seeing', detecting a pattern of matter, e.g. sound)? In a sense, not moving at all or both moving at the same maximum speed don't seem to be much different, from the 'perspective' of a photon. Somewhat related, this video describes how, if one could travel on a vehicle that could accelerate at a constant rate continuously for decades, one would eventually see the cosmic microwave background radiation as a rainbow ring because traveling closer and closer to the speed of light would shift the apparent frequency of the radiation first into the visible spectrum (and then beyond it).
- jvanderbot 7y agoIt's not about latency, it's about power required to transmit. From far away, you need to push lots of power through to get a readable signal on the receiver side. It's kinda-sorta like seeing a flashlight.
- johnhenry 7y agoDon't get your hopes down! It's still very possible that we'll get some good, if not real-time, video out of this!
- jvanderbot 7y agoAh, we likely will not get real time video. Maybe APL has some tricks I'm not privy to. Source: I asked a DSN coms engineer.
- swebs 7y agoThere will be at least an hour delay. Saturn is pretty far
- bdamm 7y ago10 seconds of video from Titan would change the world. It's shame we don't have this from Mars already. So it would take a few weeks to transmit - we got time. Now figuring out which 10 seconds to select and send to earth... that'll be interesting. An on-board cache of x GB data storage, with key frames taken every 30 minutes, would probably be able to select some pretty compelling 10 second segments.
- AmericanChopper 7y agoWhat about the world would be different after getting a 10 second video from Titan?
- cheerlessbog 7y agoIt would be inspiring for me at least.(Assuming something was moving)
- andygates 7y agoSend them all, just pick a likely-nice one for sending while the eyes of the world are on Mission Control. Caching everything then sending it at leisure is working nicely for New Horizons.
- T-hawk 7y agoFrom a scientific standpoint, there's really no value in downlinking video as opposed to still images. It costs several multiples worth of scarce downlink bandwidth, for a tiny gain in what there is to see of the same rocks at slightly different angles. Same reason we didn't have New Horizons at Pluto or the various Mars rovers do any video.
- martinald 7y agoWhy is bandwidth so scare still? Satellites in geosynchronous orbit on earth can do terabit/sec of total capacity now. Obviously latency is going to be extremely high, but I can't really understand why data rates are still so low?
- jvanderbot 7y ago"one over r-squared" Latency is high, but the power you have to pump through an antenna / laser to get enough watts on the receiver goes up really fast with distance. Here's a summary that touches on it if you'd like to learn more: http://www.qrg.northwestern.edu/projects/vss/docs/Communications/2-why-does-data-transfer-rate-drop-with-distance.html http://www.qrg.northwestern.edu/projects/vss/docs/Communicat... And here's a detailed derivation for voyager. https://space.stackexchange.com/questions/24338/how-to-calculate-data-rate-of-voyager-1 https://space.stackexchange.com/questions/24338/how-to-calcu...
- SomeHacker44 7y agoLow transmit power. Long distance. Very low SNR at receiver.
- pdonis 7y agoBecause the signals have to travel so much farther and are so much weaker when they arrive. It's amazing that any data at all can be extracted from a radio signal that travels a billion miles.
- zild3d 7y agoInverse square law. For the same transmit power, your received signal strength diminishes with the square of the distance That received signal strength is what determines channel capacity (C) which is the upper limit on the bit rate you can get. see Friis and Shannon's channel capacity [0] https://en.wikipedia.org/wiki/Friis_transmission_equation https://en.wikipedia.org/wiki/Friis_transmission_equation [1] https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theore...
- cwkoss 7y agoIn addition to lack of solar energy, I wonder if nuclear power source is necessary to keep batteries or other electronics warm enough to function properly. Conversely, on Titan, we won't need to worry about heat sinks as everything is kept at ~94K in a bath of liquid and frozen methane. Perhaps in a few hundred years AWS's most popular region for intensive compute will be under Titan's methane sea. High spin up cost, but cheap super-conduction environment once you're up.
- rzimmerman 7y agoThat's a good point - the "waste" heat from an RTG (which is only about 5% efficient) is very useful in those extreme cold temperatures.
- greglindahl 7y agoNASA makes a smaller RTGs for heating tasks, they can scale smaller if they don’t need to generate electricity.
- saagarjha 7y agoSuper fast compute, but awful ping…
- newsoul2019 7y agoPerfect for mining bitcoin
- redcalx 7y agoNot really; if you find a block it will mostly likely have been beaten by someone else's block by the time yours reaches most nodes...unless there is a Saturn based side chain or similar.
- heavenlyblue 7y agoIt depends if the "most nodes" are on Mercury or on Earth.
- p1mrx 7y agoWill this be the first-ever instance of nuclear-powered flight?
- sandworm101 7y agoNo. >> The Pentagon is aware of a Russian test of a nuclear-powered cruise missile but the system is still under development and had crashed in the Arctic in 2017.[17][18][19] A RAND Corporation researcher specializing in Russia said "My guess is they're not bluffing, that they've flight-tested this thing. But that's incredible." https://en.wikipedia.org/wiki/Nuclear-powered_aircraft#Russian_programs https://en.wikipedia.org/wiki/Nuclear-powered_aircraft#Russi... https://en.wikipedia.org/wiki/9M730_Burevestnik https://en.wikipedia.org/wiki/9M730_Burevestnik
- nickserv 7y agoThis case is different though, using the fission reaction to generate electricity which in turn powers the electric motors among other things. The nuclear powered missiles use the fission reaction to heat incoming air similar to how a jet engine works.
- Sharlin 7y agoNo fission reaction, just radioactive decay in Dragonfly's case. It will use an RTG (radioisotope thermoelectric generator) not unlike Curiosity and most missions to the outer planets to date.
- thatcherc 7y agoJust a note - radioactive decay is is fission, since it involves a nucleus splitting apart.
- Sharlin 7y agoNo, not quite. One of the types of radioactive decay is spontaneous fission, but it's not relevant in the context of RTGs. Alpha decay (the emission of a 4He nucleus) might in principle be called "fission" but in practice is not. Beta decay involves no splitting whatsoever.
- binarymax 7y agoHow does one test on earth, a drone for a different atmospheric and gravitational environment? Some great drone simulation techniques are going to come out of this project.
- dev_tty01 7y agoNo problem. Large atmospheric chamber or controlled wind tunnel. Pump the pressure up or down, change the gas mixtures, whatever. Gravity, partially support the drone's weight. NASA is good at this stuff.
- nradov 7y agoYes that's how they tested the Mars drone. https://www.jpl.nasa.gov/news/news.php?feature=7417 https://www.jpl.nasa.gov/news/news.php?feature=7417
- mdorazio 7y agoI kind of wish it had an airship counterpart. Inflating a dirigible there would take advantage of the same atmosphere + gravity benefits with the added bonus of not needing constant power to move around.
- EForEndeavour 7y agoGood point: I seriously wonder if they considered a dirigible design. Buoyancy + directional propulsion does seem simpler in my space-novice opinion compared to a quadcopter. A blimp would be slower than a quadcopter, but nobody's going to be piloting the thing in real time, so that shouldn't matter.
- jvanderbot 7y agoYes, that was a mission proposal years ago, a blimp and quads. It was not selected then or rehashed this time. In addition, a blimp only concept has been floated (ha!) as well.
- deeth_starr_v 7y agoBlimp only wouldn't be able to take ground samples easily
- nsxwolf 7y agoWhat about hydrogen fuel cells? Isn't the whole place basically nothing but fuel?
- jvanderbot 7y agoThose work by combining H with O. Not much available oxygen there.
- gene-h 7y agoit's all fuel, but there's no oxidizer
- samstave 7y agoWhy arent we just mass launching probes to all the planets? Serious question: Why is it not OK to have a standard sensor array on every planet in the solar system?
- krapp 7y ago> Why arent we just mass launching probes to all the planets? Because we don't live in a fictional sci-fi universe where launching things into space doesn't cost a ridiculous amount of money, time and effort, and can't only be done at certain times from certain locations in order to get the orbits right, or where years of effort and millions of dollars (or whatever currency) don't also go into building the things to be launched into space. The world has better things to spend its money on. >Why is it not OK to have a standard sensor array on every planet in the solar system? What is a "standard sensor array?" We've already sent a lot of probes to a lot of places[0] around the solar system. But read the rest of this thread - it's a lot more complicated than it seems. Also, remember how hostile and difficult the solar system can be. Jovian planets don't even have a solid surface to be "on," for instance, and Venus has a pressure of 90 atmospheres and it rains sulfuric acid. [0]https://en.wikipedia.org/wiki/List_of_landings_on_extraterrestrial_bodies https://en.wikipedia.org/wiki/List_of_landings_on_extraterre...
- andygates 7y agoTo the second question: since each mission is expensive and time-consuming, scientists reasonably want the best sensors for each mission. That's both the tech upgrade during the n-year coast phase, and the investigation upgrade as they work out new things to investigate. It's not as straightforward as spamming the system with cameras. That's bound to happen more, after the MarCO cubesats had success flying along with Insight.
- bduerst 7y agoProbably a dumb question, but how does the nuclear source work? Nuclear powerplants work by heating steam to turn a turbine. This drone won't have heavy water reservoirs so how does it convert the fission heat into electricity? Stirling engine?
- Gibbon1 7y agoMost nuclear power sources for space stuff works by Peltier effect. See Radioisotope thermoelectric generator. radio-isotope decay -> heat -> Peltier stack -> electricity. Advantages: no moving parts, no vibration, infinitesimal mass change, exceedingly reliable. 'Small' Disadvantage: Efficiency kinda crummy at ~5%. Slowly loses output as fuel decays and the Peltier stack degrades.
- petascale 7y agoProbably an RTG [1], it's what NASA normally uses. It's thermoelectric [2]: Heat (in this case from radioactive decay) is converted directly into electricity without moving parts. [1] https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge... [2] https://en.wikipedia.org/wiki/Thermoelectric_effect#Seebeck_effect https://en.wikipedia.org/wiki/Thermoelectric_effect#Seebeck_...
- ekianjo 7y agoJust like nuclear sources work on sattelites. You produce heat with fission or nuclear degradation and then thermoelectric conversion.
- pfarnsworth 7y agois there no wind on Titan? What if there's a windstorm and it crashes the drone? At least a vehicle could resist crashing, unlike a drone.